The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. A method currently exists for recording acceleration and deceleration (analog) events and discrete electrical signals (digital) for various munitions. This method consists of assembling three main items. These items are the actual data recorder in the form of a processor, a power source, and an acceleration sensor or sensors. As seen in FIG. 1, all three of these components are typically electrically connected with wires.
Sometimes, the data recorder, power source, and acceleration sensor or combinations of these components are installed in a separate housing instead of “floating” inside an available cavity. In this case, the separate housing is typically filled with wax and/or glass beads or equivalent supporting media. In some cases, cabling/wires that extend outside of the test article are connected to some/all of the components for power and communication. In general, it is difficult to assemble the items discussed above due to the fact that these items are generally placed in a munition as an afterthought. Often, these assemblies are rather unsophisticated and use, for example, wooden dowels and tape have been used to assemble the battery, data recorder, and sensor together prior to placement into a warhead. Subsequent installation of the wax/glass beads, to increase the likelihood the assembly will survive, leads to significant room for error, i.e. insufficient fill leading to movement of components resulting in broken wires. Wax/glass beads are messy to work with and typically require clean up of the work area after initial installation. Disassembly of the items from the projectile is also challenging. Often wires will break during disassembly, possibly leading to component damage and, more importantly, the loss of test data stored in volatile memory.
In the prior art system discussed above, the data recorder starts to acquire and permanently store data after it has received an external signal. This signal can be caused, for example, by a circuit that is closed (or opened) after a munition is launched or impacts a surface. The circuit is typically closed (or opened) by way of an acceleration sensing switch composed of a mass, a spring and an electrical contact(s). When the acceleration becomes large enough, the mass overcomes the counteracting force from the spring thus closing (or opening) the circuit through the electrical contact(s).
Most current data recorders require power to be applied to the data recorder at all times during and after the event of interest. If power to the data recorder module is lost at any time, all the data is lost. This is due to what is known as “volatile memory” or memory that requires power to be maintained after it has been recorded. For current data recorders that use non volatile (EEPROM or flash based) memory, any loss in power during an impact event causes a complete loss of data. This occurs because the data is not actually permanently recorded onto the non-volatile memory until the end of the event. Memory write speeds prevents the “real time” recording of this data in EEPROM during an actual impact event. Additionally, current data recorders rely on only one trigger event to start the recording sequence. This means that a false/premature trigger event can lead to capturing erroneous data.
As such, the current data recording prior art systems offer the following disadvantages: 1) Items are placed in a munition as an “after thought” causing improperly supported assemblies leading to an increased risk of broken wires and data recorder component damage; 2) Difficulty installing and controlling the supporting fill, leading to possible movement of components, thus leading to broken components/wires; 3) Failure of the external power source, i.e. a broken battery leads during an impact event lead to partial or total loss of data; 4) Disassembly can cause components to be damaged, power to be lost, and requires clean up due to wax/glass beads; 5) Momentary/permanent loss of power for volatile memory and EEPROM/Flash non volatile memory to the data recorder (i.e. broken power wire, damaged battery etc.) can lead to total loss of data; and 6) A premature trigger event can lead to incorrect data being permanently recorded.
It is an object of the present teachings to provide a data recording assembly for munitions that integrates the power source, data recorder, and sensors in a package that overcomes at least one of these problems above. Additionally this data recorder contains features that are intended to increase the probability that as much data as possible will be recovered after an impact event. These features and a general description of the device are discussed below.